The abiotic and biotic controls of arctic lake food webs in a changing climate
My dissertation research pursued questions pertaining to the abiotic and biotic controls of arctic lake food webs, and the direct and indirect effects of climate warming on arctic fishes and lake ecosystems-- I addressed these questions with a mix of field, lab, and modeling approaches in conjunction with the National Science Foundation's Arctic Long Term Ecological Research site, based out of Toolik Field Station.
Lakes are sensitive to the surrounding climate and can respond rapidly to change. Arctic lakes may be particularly vulnerable to climate change due to overall low productivity and species diversity, and further, the Arctic is warming faster than any other region of the globe. While we can predict how fishes might respond to a warmer climate, we require a better understanding of 1) how their food resources (e.g., zooplankton) may respond; and, 2) how interannual variability (e.g., growing season length or ice-free period) may affect fish growth and condition, especially going into and coming out of harsh arctic winters. I sought to improve our understanding of these areas through a combination of experimentation, observation (including long-term data), and modeling. |
Further, on the North Slope, Alaska, geomorphic constraints of the landscape generally regulate fish community distribution of relatively few species. However, beyond this coarse filter, there is a surprising amount of variation in trophic structure (e.g., top predator, maximum size) given the low species diversity. Trophic structure is likely a function of complex interactions that are partially determined by surface water connectivity. In the face of a changing climate, predictable patterns of lake trophic structure may become unpredictable and new fish community structures may emerge.
To better understand these structures and patterns, I am used a suite of tools including stable isotopes, genetics, and eDNA to extend our predictions to lakes across the North Slope. See below for publications and check back often...much more to come! |
Using experimental and long-term data to predict invertebrate prey biomass and availability in arctic lakes.
Evidence of the applicability of using environmental DNA to quantify the abundance of fish populations in natural lentic waters with additional sampling considerations
Relationships between A) fish abundance (top), B) density by area (bottom left), and C) density by volume (bottom right) and mean eDNA concentration (copies·L-1) across five study lakes in northern Alaska sampled in 2016. Note: density by area and density by volume relationships are back-transformed from log(eDNA concentration).
Klobucar, S.L., T. Rodgers, and P. Budy. 2017. At the forefront: evidence of the applicability of using environmental DNA to quantify the abundance of fish populations in natural lentic waters with additional sampling considerations. Canadian Journal of Fisheries and Aquatic Sciences 74(12): 2030 - 2034.
See also: Rodgers, T., J.R. Olson, S.L. Klobucar, and K.E. Mock. 2017. Quantitative PCR assays for detection of five Alaskan fish species: Lota lota, Salvelinus alpinus, Salvelinus malma, Thymallus arcticus, and Cottus cognatus from environmental DNA. Conservation Genetics Resources. |
Environmental DNA (eDNA) sampling has proven to be a valuable tool for detecting species in aquatic ecosystems. Within this rapidly evolving field, a promising application is the ability to obtain quantitative estimates of relative species abundance based on eDNA concentration rather than traditionally labor-intensive methods. We investigated the relationship between eDNA concentration and arctic char (Salvelinus alpinus) abundance in five well-studied natural lakes, and additionally, we examined the effects of different temporal (e.g., season) and spatial (e.g., depth) scales on eDNA concentration. Concentrations of eDNA were linearly correlated with char population estimates (R^2= 0.78) and exponentially correlated with char densities (R^2= 0.96 by area; 0.82 by volume). Across lakes, eDNA concentrations were greater and more homogeneous in the water column during mixis; however, when stratified, eDNA concentrations were greater in the hypolimnion. Overall, our findings demonstrate that eDNA techniques can produce effective estimates of relative fish abundance in natural lakes. These findings can guide future studies to improve and expand eDNA methods while informing research and management using rapid and minimally invasive sampling.
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The morphological and genetic diversity of arctic char populations in arctic Alaska
Polymorphism allows divergent morphs (e.g., phenotypes) of the same species to coexist by minimizing intraspecific competition, especially when resources are limiting. Arctic char are described as one of the most versatile vertebrates in the world, and accordingly, morphologically and genetically divergent morphs are extremely common. In the face of a changing climate, populations of char can be expected to adapt to changing conditions to maximize fitness and persistence; however, to be successful, these adaptive changes must minimally match the rate of environmental change. In this study, we investigated the morphological and genetic diversity of seven populations of arctic char across two distinct lake groups with different size structures (e.g., mean, maximum total length).
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The abiotic and biotic factors that structure lake food webs with populations of arctic char in arctic Alaska
[cover photo: a Toolik staple under the midnight sun-- the lakeside sauna (not pictured: slide for lake entry)]